Any short American Style option can be assigned before it stops trading. Option assignments are a double random lottery, so you could get assigned on one or all of the open short American style options in your account before the short option expires. The earliest you would see an assignment to the account is after the IBKR system overnight refresh is completed sometime between midnight and 2 AM EST. Option assignments are processed overnight and a notification is sent to the account's Message Center as soon as the assignments are processed into an account. In the most recent TWS builds an assignment transaction will be shown in the Classic TWS Trade Log even though assignments and exercises are not trades but closing transactions.
In a scenario where the account holds an open, in-the-money, vertical spread, it is your responsibility to exercise the long leg of the spread in order to close any stock delivered from an overnight short option assignment. You can use the Option Exercise Tool (available in the premarket hours) to exercise your In-the-Money long US stock option. To immediately exercise the option and have the underlying stock delivered into your account, you can check the "Make Final" box when submitting the exercise request. This makes the request non-editable and non-cancelable, allowing for immediate closing of the option position and delivery of the shares. You can also enter a closing stock limit order (available in the premarket hours) in order to close an assigned stock position fully or partially. If the account is assigned stock overnight and the account is in a margin deficit it may be subject to liquidation.
Additional Information
- Disclosure Regarding Interactive Brokers' Procedures for Allocating Equity Option Assignment Notices from OCC
- Why am I not informed of the assignment on my US securities option position until the following day?
- Will the long leg of an option spread be automatically exercised before expiration if the short is assigned?